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[USN-8834-1] Exim vulnerabilities

Posted on 28 September 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8834-1
September 28, 2026

exim4 vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

Several security issues were fixed in Exim.

Software Description:
- exim4: Exim is a mail transport agent

Details:

It was discovered that Exim had an out-of-bounds write when
Proxy-Protocol was used with an attacker-controlled proxy. A remote
attacker could possibly use this issue to execute arbitrary code.
(CVE-2026-94054)

It was discovered that Exim had a use-after-free when certain
non-default TLS settings were used with GnuTLS. A remote attacker
could possibly use this issue to cause Exim to crash, resulting in
a denial of service. This issue only affected Ubuntu 26.04 LTS.
(CVE-2026-94055)

It was discovered that Exim allowed attackers to read uninitialized
data from stack memory when Proxy-Protocol was used with an
attacker-controlled proxy. A remote attacker could possibly use this
issue to obtain sensitive information. (CVE-2026-94056)

It was discovered that Exim allowed SMTP smuggling via crafted data
sent after a rejection during DATA processing. A remote attacker
could possibly use this issue to inject arbitrary email messages.
(CVE-2026-94057)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
exim4 4.99.1-1ubuntu1.5

Ubuntu 24.04 LTS
exim4 4.97-4ubuntu4.8

Ubuntu 22.04 LTS
exim4 4.95-4ubuntu2.12

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8834-1
CVE-2026-94054, CVE-2026-94055, CVE-2026-94056, CVE-2026-94057

Package Information:
https://launchpad.net/ubuntu/+source/exim4/4.99.1-1ubuntu1.5
https://launchpad.net/ubuntu/+source/exim4/4.97-4ubuntu4.8
https://launchpad.net/ubuntu/+source/exim4/4.95-4ubuntu2.12

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